Blender Camera Controls Stopped Working
Just had the exact thing happen to me and fixed it in last ditch effort. Phew

Can't re-trace my steps exactly to emulate the problem, however the fix is still fresh. Screen Split 3D viewport in two, in the new viewport I hit numpad 0 and from there navigating the virtual cam - Shift pan and Ctrl zoom - seemed to return the initial viewport back to functioning as it should.

Would love to know how that happened in the first place. Did I accidentally hit a slider or dropdown? Or is this a bug?